Calculations on a Ducted Propeller : 2nd Report : The Flow Around an Unsymmetric Ducted Propeller in the Non-uniform Wake

Abstract

In this report, the flow around an unsymmetric ducted propeller in the non-uniform wake is calculated theoretically on the basis of the thought similar to the previous paper. The assumptions used here are as follows. (1) The number of propeller blade is infinity. (2) The free vortex is shed out only at the tip of the propeller blade. (3) The induced velocity of the propeller can be approximated by the induced velocity obtained from a quasi-static calculation. (4) The thickness of the nozzle is negligible. By numerical study based on the above theoretical calculations, next points become clear. (1) The velocity of flow relative to the nozzle at its upper part is very small and it is able to suppose that a negative relative velocity arises at that part. (2) The effect to make a flow uniform inside a nozzle becomes large in a ducted propeller having a nozzle of a large nose angle or diffuser angle at the upper part of it. (3) The efficiency of an unsymmetric ducted propeller with a nozzle of large nose or diffuser angle at the upper part of it is better than the efficiency of a symmetric ducted propeller in the non-uniform wake. (4) The thrust of the nozzle in the non-uniform wake is smaller than the thrust in uniform flow of the same mean inflow velocity.